Biology subjects

Castellanos, A.

Publications and source records attributed to Castellanos, A..

7 recordsLinked to original sources

bioRxiv2026

Rethinking the movement ecology of Andean bears: temperature-driven cathemerality and seasonal space-use cycles

BackgroundThe Andean bear (Tremarctos ornatus), South Americas only ursid, is one of the worlds most elusive large mammals, making movement data collection exceptionally rare. Addressing this gap, we present the largest telemetry dataset ever assembled, spanning 19 individuals tracked across three Ecuadorian National Parks over two decades, paired with a novel analytical approach. MethodsWe integrated Continuous-Time Movement Models (CTMM), Auto-correlated Kernel Density Estimates (AKDEs), Hidden Markov Models (HMM) and a diel niche theoretical framework to mitigate biases previously unaccounted for the species in telemetry studies. Fine-scale AKDEs and non-linear movement metrics were calculated to understand seasonal space use and movement behaviors. Speed and diffusion from CTMM and behavioral states from HMM were modelled with environmental covariates to investigate which conditions shape diel and seasonal activity. ResultsPopulation mean home range was 138.2 km2 (95% Confidence Intervals 78.7-225.5), with males (239.8 km2, 182.8-307.5), significantly exceeding females (58.5 km2, 35.5-90.3). Notably, three females exhibited ranges comparable to some males. Weekly and monthly AKDEs uncovered cyclic home range dynamics potentially driven by resource availability, with contractions around corn harvests and berry seasons, and expansions during paramo transitions. Decoupling speed from diffusion rates showed region-specific behaviors: intensive patch exploitation in Llanganates, broad exploratory ranging in Cayambe-Coca, and suppressed female locomotion in Cotacachi-Cayapas. Statistical analyses identified temperature as a key diel modulator and precipitation as the seasonal driver. Foraging probability increased between 2:00-6:00, large displacements between 7:00-14:00, and nocturnal movement rose significantly under colder conditions. Across diel hypothesis frameworks, bears were classified as cathemeral rather than strictly diurnal, corroborated by camera-trap records from Colombia, Ecuador, and Peru. ConclusionsWe propose a cathemeral diel phenotype that responds to thermal fluctuations and situates Andean bears within a broader ursid context of thermoregulatory niche plasticity. This dataset reveals unprecedented resolution of regional and sex specific behaviors that will facilitate and accelerate comparative studies in rapidly changing Andean landscapes. By releasing this long-term dataset as an open resource, we provide a foundation for climate-resilient conservation strategies. More broadly, we advocate for data democratization and invite collaboration.

ecology↗

bioRxiv2026

Endothelial Cell Secretome Alterations Induced by Inflammatory Stress

Endothelial cells detect pathogens through pattern recognition receptors, such as Toll-like receptor 4 (TLR4), which triggers the synthesis and secretion of molecules that initiate the innate immune response. Proteins bearing signal peptides are secreted through the classical endoplasmic reticulum (ER)-Golgi-dependent route, whereas select signal-peptide-lacking cytoplasmic proteins are secreted via less well-characterized ER-Golgi-independent mechanisms, collectively termed unconventional cytoplasmic protein secretion (UCPS). To systematically characterize the secretome of human umbilical vein-derived endothelial cells (HUVECs) and delineate the contribution of UCPS, we performed deep quantitative proteomics on HUVEC cell lysates and conditioned medium before and after TLR4 stimulation with lipopolysaccharide (LPS). Of 5205 proteins detected in either fraction, 381 were enriched in the conditioned medium and therefore classified as secreted. Of these, 333 proteins (87.4%) were secreted via the conventional pathway, and 48 (12.6%) were secreted via UCPS, 43 of which were not previously associated with this process. Predicted functions of UCPS-secreted proteins include redox regulation, proteostasis, cytoskeletal remodeling, and innate immune signaling. We confirmed that -globin (HBA1), which functions as a redox sensor and regulator of nitric oxide in endothelial cells, is secreted constitutively by UCPS and at higher levels following inflammatory activation. Notably, UCPS cargo identity showed poor concordance with current computational predictors, underscoring the need for empirical datasets. Overall, our findings suggest that the HUVEC secretome includes both conventionally and unconventionally secreted proteins that regulate coagulation, angiogenesis, and immune function. Our findings establish a high-quality secretome dataset for HUVECs, providing a novel resource for future efforts to define the molecular determinants governing UCPS cargo selection and trafficking related to endothelial cell function.

cell biology↗

bioRxiv2024

Influence of salinity on the thermal tolerance of aquatic organisms

Aquatic organisms are challenged by changes in the external environment, such as temperature and salinity fluctuations. The response of an organism to temperature changes can be modified by salinity, thus pointing at the potential interaction of both variables. In the present study, we tested this assumption for freshwater, brackish, and marine organisms, including algae, macrophytes, heterotrophic protists, parasites, invertebrates, and fish. We reviewed the existing body of literature on potential interactions between temperature and salinity and performed a meta-analysis that compared the thermal tolerance (characterized by the temperature optima, lower and upper temperature limits, and thermal breadths). The final database includes 90 relevant publications (algae: 15; heterotrophic protists: 1; invertebrates: 43; and fish: 31). Relevant publications for microphytes and parasites were not available. Overall, our results show that decreasing salinity significantly increased the lower temperature limits and decreased the upper temperature limits irrespective of the organism groups. These findings mainly reflect the response to salinity changes in brackish and marine systems that dominate our database. Although the number of studies on freshwater species was limited, they showed negative, although statistically nonsignificant, effects of an increased salinity on the thermal tolerance of these species (i.e. increased lower limits and decreased upper limits). In addition, our meta-analysis shows nonsignificant differences in the responsiveness of thermal tolerance to salinity changes among different groups of organisms, but the sensitivity of thermal tolerance to salinity changes generally followed the order: algae > invertebrates > fish. Facing the impact of climate change, our findings point at adverse effects of salinity changes on the temperature tolerance of aquatic organisms. Further studies that investigate the thermal performance of freshwater species at various salinity gradients are required to broaden the evidence for interactions between salinity and temperature tolerance. This also applies to the influence of parasitic infections, which have been found to modulate the temperature tolerance of aquatic invertebrates and fish.

ecology↗

bioRxiv2024

BETA-HYDROXYBUTYRATE COUNTERACTS THE DELETERIOUS EFFECTS OF A SATURATED HIGH-FAT DIET ON SYNAPTIC AMPA RECEPTORS AND COGNITIVE PERFORMANCE

The ketogenic diet, characterized by high fat and low carbohydrates, has gained popularity not only as a strategy for managing body weight but also for its efficacy in delaying cognitive decline associated with neurodegenerative diseases and the aging process. Since this dietary approach stimulates the livers production of ketone bodies, primarily {beta}-hydroxybutyrate (BHB), which serves as an alternative energy source for neurons, we investigated whether BHB could mitigate impaired AMPA receptor trafficking, synaptic dysfunction, and cognitive decline induced by metabolic challenges such as saturated fatty acids. Here, we observe that, in cultured primary cortical neurons, exposure to palmitic acid (200M) decreased surface levels of glutamate GluA1-containing AMPA receptors, whereas unsaturated fatty acids, such as oleic acid and {omega}-3 docosahexaenoic acid (200M), and BHB (5mM) increased them. Furthermore, BHB countered the adverse effects of palmitic acid on synaptic GluA1 levels in hippocampal neurons, as well as excitability and plasticity in hippocampal slices. Additionally, daily intragastric administration of BHB (100 mg/kg/day) for two months reversed cognitive impairment induced by a saturated high-fat diet (49% of calories from fat) in a mouse experimental model of obesity. In summary, our findings underscore the significant impact of fatty acids and ketone bodies on AMPA receptors abundance, synaptic function and neuroplasticity, shedding light on the potential use of BHB to delay cognitive impairments associated with metabolic diseases.

neuroscience↗

bioRxiv2023

The search behavior of terrestrial mammals

Animals moving through landscapes need to strike a balance between finding sufficient resources to grow and reproduce while minimizing encounters with predators 1,2. Because encounter rates are determined by the average distance over which directed motion persists 1,3-5, this trade-off should be apparent in individuals movement. Using GPS data from 1,396 individuals across 62 species of terrestrial mammals, we show how predators maintained directed motion ~7 times longer than for similarly-sized prey, revealing how prey species must trade off search efficiency against predator encounter rates. Individual search strategies were also modulated by resource abundance, with prey species forced to risk higher predator encounter rates when resources were scarce. These findings highlight the interplay between encounter rates and resource availability in shaping broad patterns mammalian movement strategies.

ecology↗

bioRxiv2021

Home range and movement patterns of the Andean Fox Lycalopex culpaeus (Molina 1782) in Cotopaxi National Park, Ecuador

This study reports movement patterns and home range estimates of an Andean fox (Lycalopex culpaeus) in Cotopaxi National Park in Ecuador, representing the first GPS-tagging of the species. The GPS functioned well during the 197-day tracking period. Home range sizes ranged between 4.9 - 8.1 km2, depending on the estimation method. Movement speeds averaged 0.17 km/hr at day vs. 0.87 km/hr. at night, and distance traveled averaged 0.23 km at day vs. 0.89 km at night. These preliminary results highlight the importance of collecting unbiased, high-quality data which enables an enhanced understanding on mammal behavior and human/animal interaction.

animal behavior and cognition↗

bioRxiv2019

TRESK background K+ channel deletion selectively uncovers enhanced mechanical and cold sensitivity

Changes in TRESK K+ channel expression/function enhance sensory neurons excitability, but its role in somatosensory perception and nociception is poorly understood. We show that TRESK regulates the sensitivity to mechanical and cold stimuli but not the perception of heat. TRESK knockout mice nociceptive neurons present an enhanced excitability; skin nociceptive C-fibers show an increased activation by lower intensity cold or mechanical stimulation and mice lacking TRESK present mechanical and cold hypersensitivity. TRESK is also involved in osmotic pain and in early phases of formalin-induced inflammatory pain, but not in the development of mechanical and heat hyperalgesia during chronic pain. In contrast, mice lacking TRESK present cold allodynia that is not further enhanced by oxaliplatin. In summary, genetic removal of TRESK uncovers enhanced mechanical and cold sensitivity, indicating that it regulates the excitability of specific neuronal subpopulations involved in mechanosensitivity and cold-sensing, acting as a brake to prevent activation by low-intensity stimuli.

neuroscience↗